The S–I cycle consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen. All other chemicals are recycled. The S–I process requires an efficient source of heat.
Iodine and any accompanying water or SO2 are separated by condensation, and the hydrogen product remains as a gas.
Net reaction: 2 H2O → 2 H2 + O2
The sulfur and iodine compounds are recovered and reused, hence the consideration of the process as a cycle. This S–I process is a chemical heat engine. Heat enters the cycle in high-temperature endothermic chemical reactions 2 and 3, and heat exits the cycle in the low-temperature exothermic reaction 1. The difference between the heat entering and leaving the cycle exits the cycle in the form of the heat of combustion of the hydrogen produced.
Completely closed system without byproducts or effluents (besides hydrogen and oxygen)
Suitable for application with solar, nuclear, and hybrid (e.g., solar-fossil) sources of heat - if high enough temperatures can be achieved
More developed than competing thermochemical processes
Scalable from relatively small scale to huge applications
No need for expensive or toxic catalysts or additives
More efficient than electrolysis of water (~70-80% efficiency) using electricity derived from a thermal power plant (~30-60% efficiency) combining to ~21-48% efficiency
Corrosive reagents used as intermediaries (iodine, sulfur dioxide, hydriodic acid, sulfuric acid); therefore, advanced materials needed for construction of process apparatus
Significant further development required to be feasible on large scale
At the proposed temperature range advanced thermal power plants can achieve efficiencies (electric output per heat input) in excess of 50% somewhat negating the efficiency advantage
In case of leakage corrosive and somewhat toxic substances are released to the environment - among them volatile iodine and hydroiodic acid
If hydrogen is to be used for process heat the required high temperatures make the benefits compared to direct utilization of heat questionable
Unable to use non-thermal or low-grade thermal energy sources such as hydropower, wind power or most currently available geothermal power
Research
The S–I cycle was invented at General Atomics in the 1970s.[1] The Japan Atomic Energy Agency (JAEA) has conducted successful experiments with the S–I cycle in the Helium cooled High Temperature Test Reactor,[2][3][4][5] a reactor which reached first criticality in 1998, JAEA have the aspiration of using further nuclear very high-temperature generation IV reactors (VHTR) to produce industrial scale quantities of hydrogen. (The Japanese refer to the cycle as the IS cycle.) Plans have been made to test larger-scale automated systems for hydrogen production. Under an International Nuclear Energy Research Initiative (INERI) agreement, the French CEA, General Atomics and Sandia National Laboratories are jointly developing the sulfur-iodine process. Additional research is taking place at the Idaho National Laboratory, in Canada, Korea and Italy.
Material challenge
The S–I cycle involves operations with corrosive chemicals at temperatures up to about 1,000 °C (1,830 °F). The selection of materials with sufficient corrosion resistance under the process conditions is of key importance to the economic viability of this process. The materials suggested include the following classes: refractory metals, reactive metals, superalloys, ceramics, polymers, and coatings.[6][7] Some materials suggested include tantalum alloys, niobium alloys, noble metals, high-silicon steels,[8] several nickel-based superalloys, mullite, silicon carbide (SiC), glass, silicon nitride (Si3N4), and others. Recent research on scaled prototyping suggests that new tantalum surface technologies may be a technically and economically feasible way to make larger scale installations.[9]
Hydrogen economy
The sulfur-iodine cycle has been proposed as a way to supply hydrogen for a hydrogen-based economy. It does not require hydrocarbons like current methods of steam reforming but requires heat from combustion, nuclear reactions, or solar heat concentrators.
^Besenbruch, G. 1982. General Atomic sulfur iodine thermochemical water-splitting process. Proceedings of the American Chemical Society, Div. Pet. Chem., 27(1):48-53.
^"HTTR High Temperature engineering Test Reactor". Httr.jaea.go.jp. Retrieved 23 January 2014.
^Status report 101 - Gas Turbine High Temperature Reactor (GTHTR300C)
^JAEA’S VHTR FOR HYDROGEN AND ELECTRICITY COGENERATION : GTHTR300C
^Paul Pickard, Sulfur-Iodine Thermochemical Cycle 2005 DOE Hydrogen Program Review
^Wonga, B.; Buckingham, R. T.; Brown, L. C.; Russ, B. E.; Besenbruch, G. E.; Kaiparambil, A.; Santhanakrishnan, R.; Roy, Ajit (2007). "Construction materials development in sulfur–iodine thermochemical water-splitting process for hydrogen production". International Journal of Hydrogen Energy. 32 (4): 497–504. doi:10.1016/j.ijhydene.2006.06.058.
^T. Drake, B. E. Russ, L. Brown, G. Besenbruch, "Tantalum Applications For Use In Scale Sulfur-Iodine Experiments", AIChE 2007 Fall Annual Meeting, 566a.
References
Paul M. Mathias and Lloyd C. Brown "Thermodynamics of the Sulfur-Iodine Cycle for Thermochemical Hydrogen Production", presented at the 68 th Annual Meeting of the Society of Chemical Engineers, Japan 23 March 2003. .
Atsuhiko TERADA; Jin IWATSUKI, Shuichi ISHIKURA, Hiroki NOGUCHI, Shinji KUBO, Hiroyuki OKUDA, Seiji KASAHARA, Nobuyuki TANAKA, Hiroyuki OTA, Kaoru ONUKI and Ryutaro HINO, "Development of Hydrogen Production Technology by Thermochemical Water Splitting IS Process Pilot Test Plan", Journal of Nuclear Science and Technology, Vol.44, No.3, p. 477–482 (2007). (PDF).
External links
Hydrogen: Our Future made with Nuclear (in MPR Profile issue 9)
Use of the modular helium reactor for hydrogen production (World Nuclear Association Symposium 2003)
February 15, 2023
sulfur, iodine, cycle, sulfur, iodine, cycle, cycle, three, step, thermochemical, cycle, used, produce, hydrogen, simplified, diagram, sulfur, iodine, cycle, cycle, consists, three, chemical, reactions, whose, reactant, water, whose, products, hydrogen, oxygen. The sulfur iodine cycle S I cycle is a three step thermochemical cycle used to produce hydrogen Simplified diagram of the sulfur iodine cycle The S I cycle consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen All other chemicals are recycled The S I process requires an efficient source of heat Contents 1 Process description 2 Characteristics 2 1 Advantages 2 2 Disadvantages 3 Research 3 1 Material challenge 4 Hydrogen economy 5 See also 6 Footnotes 7 References 8 External linksProcess description EditH2O O2 I2 Reaction 1 SO2 H2O Separate 2HI Separate H2SO4 Reaction 2 H2The three reactions that produce hydrogen are as follows I2 SO2 2 H2O heat 2 HI H2SO4 120 C 250 F Bunsen reaction The HI is then separated by distillation or liquid liquid gravitic separation 2 H2SO4 heat 2 SO2 2 H2O O2 830 C 1 530 F The water SO2 and residual H2SO4 must be separated from the oxygen byproduct by condensation 2 HI heat I2 H2 450 C 840 F Iodine and any accompanying water or SO2 are separated by condensation and the hydrogen product remains as a gas Net reaction 2 H2O 2 H2 O2The sulfur and iodine compounds are recovered and reused hence the consideration of the process as a cycle This S I process is a chemical heat engine Heat enters the cycle in high temperature endothermic chemical reactions 2 and 3 and heat exits the cycle in the low temperature exothermic reaction 1 The difference between the heat entering and leaving the cycle exits the cycle in the form of the heat of combustion of the hydrogen produced Characteristics EditAdvantages Edit All fluid liquids gases process therefore well suited for continuous production High thermal efficiency predicted about 50 Completely closed system without byproducts or effluents besides hydrogen and oxygen Suitable for application with solar nuclear and hybrid e g solar fossil sources of heat if high enough temperatures can be achieved More developed than competing thermochemical processes Scalable from relatively small scale to huge applications No need for expensive or toxic catalysts or additives More efficient than electrolysis of water 70 80 efficiency using electricity derived from a thermal power plant 30 60 efficiency combining to 21 48 efficiency Waste heat suitable for district heating if cogeneration is desiredDisadvantages Edit Very high temperatures required at least 850 C 1 560 F unachievable or difficult to achieve with current pressurized water reactors or concentrated solar power Corrosive reagents used as intermediaries iodine sulfur dioxide hydriodic acid sulfuric acid therefore advanced materials needed for construction of process apparatus Significant further development required to be feasible on large scale At the proposed temperature range advanced thermal power plants can achieve efficiencies electric output per heat input in excess of 50 somewhat negating the efficiency advantage In case of leakage corrosive and somewhat toxic substances are released to the environment among them volatile iodine and hydroiodic acid If hydrogen is to be used for process heat the required high temperatures make the benefits compared to direct utilization of heat questionable Unable to use non thermal or low grade thermal energy sources such as hydropower wind power or most currently available geothermal powerResearch EditThe S I cycle was invented at General Atomics in the 1970s 1 The Japan Atomic Energy Agency JAEA has conducted successful experiments with the S I cycle in the Helium cooled High Temperature Test Reactor 2 3 4 5 a reactor which reached first criticality in 1998 JAEA have the aspiration of using further nuclear very high temperature generation IV reactors VHTR to produce industrial scale quantities of hydrogen The Japanese refer to the cycle as the IS cycle Plans have been made to test larger scale automated systems for hydrogen production Under an International Nuclear Energy Research Initiative INERI agreement the French CEA General Atomics and Sandia National Laboratories are jointly developing the sulfur iodine process Additional research is taking place at the Idaho National Laboratory in Canada Korea and Italy Material challenge Edit The S I cycle involves operations with corrosive chemicals at temperatures up to about 1 000 C 1 830 F The selection of materials with sufficient corrosion resistance under the process conditions is of key importance to the economic viability of this process The materials suggested include the following classes refractory metals reactive metals superalloys ceramics polymers and coatings 6 7 Some materials suggested include tantalum alloys niobium alloys noble metals high silicon steels 8 several nickel based superalloys mullite silicon carbide SiC glass silicon nitride Si3N4 and others Recent research on scaled prototyping suggests that new tantalum surface technologies may be a technically and economically feasible way to make larger scale installations 9 Hydrogen economy EditThe sulfur iodine cycle has been proposed as a way to supply hydrogen for a hydrogen based economy It does not require hydrocarbons like current methods of steam reforming but requires heat from combustion nuclear reactions or solar heat concentrators See also EditCerium IV oxide cerium III oxide cycle Copper chlorine cycle Hybrid sulfur cycle High temperature electrolysis Iron oxide cycle Zinc zinc oxide cycleFootnotes Edit Besenbruch G 1982 General Atomic sulfur iodine thermochemical water splitting process Proceedings of the American Chemical Society Div Pet Chem 27 1 48 53 HTTR High Temperature engineering Test Reactor Httr jaea go jp Retrieved 23 January 2014 https smr inl gov Document ashx path DOCS 2FGCR Int 2FNHDDELDER pdf Progress in Nuclear Energy Nuclear heat for hydrogen production Coupling a very high high temperature reactor to a hydrogen production plant 2009 Status report 101 Gas Turbine High Temperature Reactor GTHTR300C JAEA S VHTR FOR HYDROGEN AND ELECTRICITY COGENERATION GTHTR300C Paul Pickard Sulfur Iodine Thermochemical Cycle 2005 DOE Hydrogen Program Review Wonga B Buckingham R T Brown L C Russ B E Besenbruch G E Kaiparambil A Santhanakrishnan R Roy Ajit 2007 Construction materials development in sulfur iodine thermochemical water splitting process for hydrogen production International Journal of Hydrogen Energy 32 4 497 504 doi 10 1016 j ijhydene 2006 06 058 Saramet info sheet Archived 14 February 2006 at the Wayback Machine T Drake B E Russ L Brown G Besenbruch Tantalum Applications For Use In Scale Sulfur Iodine Experiments AIChE 2007 Fall Annual Meeting 566a References EditPaul M Mathias and Lloyd C Brown Thermodynamics of the Sulfur Iodine Cycle for Thermochemical Hydrogen Production presented at the 68 th Annual Meeting of the Society of Chemical Engineers Japan 23 March 2003 PDF Atsuhiko TERADA Jin IWATSUKI Shuichi ISHIKURA Hiroki NOGUCHI Shinji KUBO Hiroyuki OKUDA Seiji KASAHARA Nobuyuki TANAKA Hiroyuki OTA Kaoru ONUKI and Ryutaro HINO Development of Hydrogen Production Technology by Thermochemical Water Splitting IS Process Pilot Test Plan Journal of Nuclear Science and Technology Vol 44 No 3 p 477 482 2007 PDF External links EditHydrogen Our Future made with Nuclear in MPR Profile issue 9 Use of the modular helium reactor for hydrogen production World Nuclear Association Symposium 2003 Retrieved from https en wikipedia org w index php title Sulfur iodine cycle amp oldid 1119876807, wikipedia, wiki, book, books, library,
